1. Field of the Invention
The present invention relates to a method of forming color images. More particularly, the present invention relates to a method of forming duplicate color images exhibiting enhanced saturation and gradation reproduction.
2. Description of the Related Art
The today widespread color photographs can be broadly classified into the color negative film, color reversal film, color instant film, etc. for shooting, and the color paper, reversal paper, display film, etc. providing prints of images recorded in the shooting materials and subjected to viewing. Among the former shooting materials, positive photosensitive materials such as a color reversal film and an instant film are dual purpose materials that are shooting materials and simultaneously can be subjected to viewing. With respect to materials for exclusive use in shooting, print materials are absolutely needed because without corresponding print materials, viewing cannot be made. In this connection, with respect to dual purpose materials as well, print materials (duplicate materials) are needed when it is intended to store precious original images or to avoid damaging original images in, for example, processing thereof as a printing original, or when there are requirements for enlargement or use of multiple duplicates.
These print materials can be broadly classified into two types. The color reversal paper and color auto positive paper comprising a reflective support and subjected to viewing with reflected light, belong to the one type. The color duplicating film and display film comprising a transparent support or translucent support and subjected to viewing with transmitted light or projection, belong to the other type. Among these, the color duplicating film is demanded to have exactly the same quality as that of an original image, since the color duplicating film can be simultaneously viewed with the original image arranged sideways. Moreover, this color duplicating film may be used as an original for printing or stored as a stock photo for a prolonged period of time. Consequently, from the viewpoint of practical use as well, it is demanded to obtain a duplicate identical with the original image. However, in reality, it is extremely difficult to reproduce exactly the same image quality because of the performance of photosensitive material, performance of printer equipment, print technology, etc.
The quality of color images is principally determined by three elements, namely, gradation reproduction, color reproduction and image quality reproduction (granularity and sharpness). Among these, the gradation reproduction is of the utmost importance for the color duplicating film demanded to realize faithful reproduction.
Furthermore, with respect to the color duplicating film, it is believed that the use of dupe films in printing, etc. should be minimized because of the deterioration of saturation and change of color from those of the original image with the exception that extinguishment of original images by cut-and-paste, retouch, etc. is anticipated. Accordingly, there has been a demand for improvement thereof. With respect to the color reversal paper as well, due to the deterioration of saturation and change of color from those of the original image, there has been a demand for improvement thereof.
Heretofore, with respect to tone reproduction, attempts aiming at faithful reproduction not accompanied by deterioration of the tone of original image have been conducted (see, for example, R. M. Evans, Principles of Color Photography, 1953). In this technical literature, there are respective descriptions for the instance where the hues of color-forming dyes of a color photosensitive material for use as an original image and a color photosensitive material for print are identical with each other, and the instance where the hues are different from each other. However, the contents thereof only present an idealized discussion separately presuming the instance where the hues are identical with each other and the instance where the hues are different from each other. There is no description regarding the technique and means for simultaneously coping with the two instances.
As means for solving these, there has been proposed a method of regulating the wavelength of maximum sensitivity in the spectral sensitivity distribution of each color sensitive layer and regulating the point gamma of characteristic curve thereof (see, for example, Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-) 9-222702). This method includes special device with respect to the spectral sensitivity of especially a red sensitive layer but is for the external system (system in which color couplers are supplied from processing solutions) whose market share is now substantially nil. In the current situation wherein the market share is substantially entirely occupied by the internal system (system in which color couplers are incorporated in photosensitive materials), the tone reproduction is unsatisfactory.
Further, in recent years, cyan couplers and magenta couplers having unfavorable absorptions reduced have been developed, and studies have been conducted for enhancing the color reproduction of photosensitive materials for shooting (see, for example, JP-A-2001-142181). Still further, the method of forming color images with the use of the same cyan coupler and same magenta coupler having unfavorable absorptions reduced in both a photosensitive material for shooting and a photosensitive material for duplication is known (see, for example, JP-A-9-222710). Desirable tone reproduction cannot be attained by this method, and hence improvements are demanded.